Demolition derby is a motorsport usually presented at county fairs and festivals. While rules vary from event to event, the typical demolition derby event consists of five or more drivers competing by deliberately ramming their vehicles into one another. The last driver whose vehicle is still operational is awarded the victory. Demolition derbies originated in the United States and quickly spread to other western nations. In Europe, this type of event is called banger racing, albeit in a demolition derby racers do not race against each other, instead aiming specifically to destroy the other cars. Demolition derbies can be very dangerous. Although serious injuries are rare, occasionally they do happen. Drivers are typically required to sign a waiver to release the promoter of an event from liability. To make the event safer, all glass is removed from the vehicle, and deliberately ramming the driver's-side door area is forbidden.